diff --git a/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache b/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache
index c5b72977cf5..ad57cffdf34 100644
--- a/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache
+++ b/modules/swagger-codegen/src/main/resources/csharp/ApiClient.mustache
@@ -4,6 +4,7 @@ using System.IO;
 using System.Linq;
 using System.Net;
 using System.Text;
+using System.Threading.Tasks;
 using Newtonsoft.Json;
 using RestSharp;
 
@@ -36,7 +37,16 @@ namespace {{invokerPackage}} {
 
     private Dictionary<String, String> defaultHeaderMap = new Dictionary<String, String>();
 
-    public Object CallApi(String Path, RestSharp.Method Method, Dictionary<String, String> QueryParams, String PostBody, 
+    public Object CallApi(String Path, RestSharp.Method Method, Dictionary<String, String> QueryParams, String PostBody,
+      Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, String> FileParams, String[] AuthSettings) {
+      var response = Task.Run(async () => {
+                            var resp = await CallApiAsync(Path, Method, QueryParams, PostBody, HeaderParams, FormParams, FileParams, AuthSettings);
+                            return resp;
+                            });
+        return response.Result;
+    }
+
+    public async Task<Object> CallApiAsync(String Path, RestSharp.Method Method, Dictionary<String, String> QueryParams, String PostBody,
       Dictionary<String, String> HeaderParams, Dictionary<String, String> FormParams, Dictionary<String, String> FileParams, String[] AuthSettings) {
 
       var request = new RestRequest(Path, Method);
@@ -67,7 +77,7 @@ namespace {{invokerPackage}} {
         request.AddParameter("application/json", PostBody, ParameterType.RequestBody); // http body (model) parameter
       }
 
-      return (Object)restClient.Execute(request);
+      return (Object) await restClient.ExecuteTaskAsync(request);
 
     }
 
diff --git a/modules/swagger-codegen/src/main/resources/csharp/api.mustache b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
index b5c8bfaeac2..6cb3178e65e 100644
--- a/modules/swagger-codegen/src/main/resources/csharp/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/csharp/api.mustache
@@ -9,10 +9,30 @@ using {{modelPackage}};
 
 namespace {{package}} {
   {{#operations}}
+
+  public interface I{{classname}} {
+    {{#operation}}
+    /// <summary>
+    /// {{summary}} {{notes}}
+    /// </summary>
+    {{#allParams}}/// <param name="{{paramName}}">{{description}}</param>{{/allParams}}
+    /// <returns>{{#returnType}}{{{returnType}}}{{/returnType}}</returns>
+    {{#returnType}}{{{returnType}}}{{/returnType}}{{^returnType}}void{{/returnType}} {{nickname}} ({{#allParams}}{{{dataType}}} {{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}});
+
+    /// <summary>
+    /// {{summary}} {{notes}}
+    /// </summary>
+    {{#allParams}}/// <param name="{{paramName}}">{{description}}</param>{{/allParams}}
+    /// <returns>{{#returnType}}{{{returnType}}}{{/returnType}}</returns>
+    {{#returnType}}Task<{{{returnType}}}>{{/returnType}}{{^returnType}}Task{{/returnType}} {{nickname}}Async ({{#allParams}}{{{dataType}}} {{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}});
+    {{/operation}}
+  }
+
   /// <summary>
   /// Represents a collection of functions to interact with the API endpoints
   /// </summary>
-  public class {{classname}} {
+  public class {{classname}} : I{{classname}} {
+
     /// <summary>
     /// Initializes a new instance of the <see cref="{{classname}}"/> class.
     /// </summary>
@@ -62,8 +82,7 @@ namespace {{package}} {
     /// <summary>
     /// {{summary}} {{notes}}
     /// </summary>
-{{#allParams}}    /// <param name="{{paramName}}">{{description}}</param>
-{{/allParams}}
+    {{#allParams}}/// <param name="{{paramName}}">{{description}}</param>{{/allParams}}
     /// <returns>{{#returnType}}{{{returnType}}}{{/returnType}}</returns>
     public {{#returnType}}{{{returnType}}}{{/returnType}}{{^returnType}}void{{/returnType}} {{nickname}} ({{#allParams}}{{{dataType}}} {{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}}) {
 
@@ -108,38 +127,40 @@ namespace {{package}} {
 	 /// <summary>
     /// {{summary}} {{notes}}
     /// </summary>
-{{#allParams}}    /// <param name="{{paramName}}">{{description}}</param>
-{{/allParams}}
+    {{#allParams}}/// <param name="{{paramName}}">{{description}}</param>{{/allParams}}
     /// <returns>{{#returnType}}{{{returnType}}}{{/returnType}}</returns>
     public async {{#returnType}}Task<{{{returnType}}}>{{/returnType}}{{^returnType}}Task{{/returnType}} {{nickname}}Async ({{#allParams}}{{{dataType}}} {{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}}) {
 
-      var _request = new RestRequest("{{path}}", Method.{{httpMethod}});
-
       {{#allParams}}{{#required}}
-      // verify the required parameter '{{paramName}}' is set
-      if ({{paramName}} == null) throw new ApiException(400, "Missing required parameter '{{paramName}}' when calling {{nickname}}");
+          // verify the required parameter '{{paramName}}' is set
+          if ({{paramName}} == null) throw new ApiException(400, "Missing required parameter '{{paramName}}' when calling {{nickname}}");
       {{/required}}{{/allParams}}
 
-      // add default header, if any
-      foreach(KeyValuePair<string, string> defaultHeader in ApiInvoker.GetDefaultHeader())
-      {
-        _request.AddHeader(defaultHeader.Key, defaultHeader.Value);
-      }
-
-      _request.AddUrlSegment("format", "json"); // set format to json by default
-      {{#pathParams}}_request.AddUrlSegment("{{baseName}}", ApiInvoker.ParameterToString({{{paramName}}})); // path (url segment) parameter
+      var path = "{{path}}";
+      path = path.Replace("{format}", "json");
+      {{#pathParams}}path = path.Replace("{" + "{{baseName}}" + "}", apiClient.ParameterToString({{{paramName}}}));
       {{/pathParams}}
-      {{#queryParams}} if ({{paramName}} != null) _request.AddParameter("{{baseName}}", ApiInvoker.ParameterToString({{paramName}})); // query parameter
+
+      var queryParams = new Dictionary<String, String>();
+      var headerParams = new Dictionary<String, String>();
+      var formParams = new Dictionary<String, String>();
+      var fileParams = new Dictionary<String, String>();
+      String postBody = null;
+
+      {{#queryParams}} if ({{paramName}} != null) queryParams.Add("{{baseName}}", apiClient.ParameterToString({{paramName}})); // query parameter
       {{/queryParams}}
-      {{#headerParams}} if ({{paramName}} != null) _request.AddHeader("{{baseName}}", ApiInvoker.ParameterToString({{paramName}})); // header parameter
+      {{#headerParams}} if ({{paramName}} != null) headerParams.Add("{{baseName}}", apiClient.ParameterToString({{paramName}})); // header parameter
       {{/headerParams}}
-      {{#formParams}}if ({{paramName}} != null) {{#isFile}}_request.AddFile("{{baseName}}", {{paramName}});{{/isFile}}{{^isFile}}_request.AddParameter("{{baseName}}", ApiInvoker.ParameterToString({{paramName}})); // form parameter{{/isFile}}
+      {{#formParams}}if ({{paramName}} != null) {{#isFile}}fileParams.Add("{{baseName}}", {{paramName}});{{/isFile}}{{^isFile}}formParams.Add("{{baseName}}", apiClient.ParameterToString({{paramName}})); // form parameter{{/isFile}}
       {{/formParams}}
-      {{#bodyParam}}_request.AddParameter("application/json", ApiInvoker.Serialize({{paramName}}), ParameterType.RequestBody); // http body (model) parameter
+      {{#bodyParam}}postBody = apiClient.Serialize({{paramName}}); // http body (model) parameter
       {{/bodyParam}}
 
+      // authentication setting, if any
+      String[] authSettings = new String[] { {{#authMethods}}"{{name}}"{{#hasMore}}, {{/hasMore}}{{/authMethods}} };
+
       // make the HTTP request
-      IRestResponse response = await restClient.ExecuteTaskAsync(_request);
+      IRestResponse response = (IRestResponse) await apiClient.CallApiAsync(path, Method.{{httpMethod}}, queryParams, postBody, headerParams, formParams, fileParams, authSettings);
       if (((int)response.StatusCode) >= 400) {
         throw new ApiException ((int)response.StatusCode, "Error calling {{nickname}}: " + response.Content);
       }